本文主要介绍external/wpa_supplicant_8/src/p2p/p2p.c文件
先看下p2p_find 这个方法
P2P_find 主要用于 P2P（点对点）网络中查找其他对等方的功能。另外可以看到设置P2P模块的状态为 P2P_SEARCH
int p2p_find(struct p2p_data *p2p, unsigned int timeout,
enum p2p_discovery_type type,
unsigned int num_req_dev_types, const u8 *req_dev_types,
const u8 *dev_id, unsigned int search_delay,
u8 seek_count, const char **seek, int freq, bool include_6ghz)
{
int res;
struct os_reltime start;
p2p_dbg(p2p, "Starting find (type=%d)", type);
//确认P2P扫描已经可以使用
if (p2p->p2p_scan_running) {
p2p_dbg(p2p, "p2p_scan is already running");
}
p2p_free_req_dev_types(p2p);
if (req_dev_types && num_req_dev_types) {
p2p->req_dev_types = os_memdup(req_dev_types,
num_req_dev_types *
WPS_DEV_TYPE_LEN);
if (p2p->req_dev_types == NULL)
return -1;
p2p->num_req_dev_types = num_req_dev_types;
}
if (dev_id) {
os_memcpy(p2p->find_dev_id_buf, dev_id, ETH_ALEN);
p2p->find_dev_id = p2p->find_dev_id_buf;
} else
p2p->find_dev_id = NULL;
p2p->include_6ghz = p2p_wfd_enabled(p2p) && include_6ghz;
if (seek_count == 0 || !seek) {
/* Not an ASP search */
p2p->p2ps_seek = 0;
} else if (seek_count == 1 && seek && (!seek[0] || !seek[0][0])) {
/*
* An empty seek string means no hash values, but still an ASP
* search.
*/
p2p_dbg(p2p, "ASP search");
p2p->p2ps_seek_count = 0;
p2p->p2ps_seek = 1;
} else if (seek && seek_count <= P2P_MAX_QUERY_HASH) {
u8 buf[P2PS_HASH_LEN];
int i, count = 0;
for (i = 0; i < seek_count; i++) {
if (!p2ps_gen_hash(p2p, seek[i], buf))
continue;
p2p_dbg(p2p, "Seek service %s hash " MACSTR,
seek[i], MAC2STR(buf));
os_memcpy(&p2p->p2ps_seek_hash[count * P2PS_HASH_LEN],
buf, P2PS_HASH_LEN);
count++;
}
p2p->p2ps_seek_count = count;
p2p->p2ps_seek = 1;
} else {
p2p->p2ps_seek_count = 0;
p2p->p2ps_seek = 1;
}
/* Special case to perform wildcard search */
if (p2p->p2ps_seek_count == 0 && p2p->p2ps_seek) {
p2p->p2ps_seek_count = 1;
os_memcpy(&p2p->p2ps_seek_hash, p2p->wild_card_hash,
P2PS_HASH_LEN);
}
//P2P_AFTER_SCAN_NOTHING表示P2P设备完成scan动作后，无需做其他动作
p2p->start_after_scan = P2P_AFTER_SCAN_NOTHING;
p2p_clear_timeout(p2p);
if (p2p->pending_listen_freq) {
p2p_dbg(p2p, "Clear pending_listen_freq for p2p_find");
p2p->pending_listen_freq = 0;
}
//停止监听
p2p->cfg->stop_listen(p2p->cfg->cb_ctx);
p2p->find_pending_full = 0;
p2p->find_type = type;
if (freq != 2412 && freq != 2437 && freq != 2462 && freq != 60480)
p2p->find_specified_freq = freq;
else
p2p->find_specified_freq = 0;
p2p_device_clear_reported(p2p);
os_memset(p2p->sd_query_no_ack, 0, ETH_ALEN);
//设置P2P模块的状态为 P2P_SEARCH
p2p_set_state(p2p, P2P_SEARCH);
p2p->search_delay = search_delay;
p2p->in_search_delay = 0;
eloop_cancel_timeout(p2p_find_timeout, p2p, NULL);
p2p->last_p2p_find_timeout = timeout;
if (timeout)
//注册一个扫描超时处理任务
eloop_register_timeout(timeout, 0, p2p_find_timeout,
p2p, NULL);
os_get_reltime(&start);
switch (type) {
case P2P_FIND_START_WITH_FULL:
if (freq > 0) {
/*
* Start with the specified channel and then move to
* scans for social channels and this specific channel.
*/
res = p2p->cfg->p2p_scan(p2p->cfg->cb_ctx,
P2P_SCAN_SPECIFIC, freq,
p2p->num_req_dev_types,
p2p->req_dev_types, dev_id,
DEV_PW_DEFAULT,
p2p->include_6ghz);
break;
}
/* fall through */
case P2P_FIND_PROGRESSIVE: //p2p_scan指向函数 wpas_p2p_scan
res = p2p->cfg->p2p_scan(p2p->cfg->cb_ctx, P2P_SCAN_FULL, 0,
p2p->num_req_dev_types,
p2p->req_dev_types, dev_id,
DEV_PW_DEFAULT, p2p->include_6ghz);
break;
case P2P_FIND_ONLY_SOCIAL:
res = p2p->cfg->p2p_scan(p2p->cfg->cb_ctx, P2P_SCAN_SOCIAL, 0,
p2p->num_req_dev_types,
p2p->req_dev_types, dev_id,
DEV_PW_DEFAULT, p2p->include_6ghz);
break;
default:
return -1;
}
if (!res)
p2p->find_start = start;
if (res != 0 && p2p->p2p_scan_running) {
p2p_dbg(p2p, "Failed to start p2p_scan - another p2p_scan was already running");
/* wait for the previous p2p_scan to complete */
if (type == P2P_FIND_PROGRESSIVE ||
(type == P2P_FIND_START_WITH_FULL && freq == 0))
p2p->find_pending_full = 1;
res = 0; /* do not report failure */
} else if (res != 0) {
p2p_dbg(p2p, "Failed to start p2p_scan");
p2p_set_state(p2p, P2P_IDLE);
eloop_cancel_timeout(p2p_find_timeout, p2p, NULL);
}
return res;
}
接着看下P2P模块的状态为 P2P_SEARCH后如何进行进入listen状态
也就是p2p_listen_in_find这个方法
static void p2p_listen_in_find(struct p2p_data *p2p, int dev_disc)
{
unsigned int r, tu;
int freq;
struct wpabuf *ies;
p2p_dbg(p2p, "Starting short listen state (state=%s)",
p2p_state_txt(p2p->state));
if (p2p->pending_listen_freq) {
/* We have a pending p2p_listen request */
p2p_dbg(p2p, "p2p_listen command pending already");
return;
}
//根据 p2p_supplicant.conf中listen_channel等配置参数获取对应的频段
freq = p2p_channel_to_freq(p2p->cfg->reg_class, p2p->cfg->channel);
if (freq < 0) {
p2p_dbg(p2p, "Unknown regulatory class/channel");
return;
}
//计算需要在listen state 等待的时间
if (os_get_random((u8 *) &r, sizeof(r)) < 0)
r = 0;
tu = (r % ((p2p->max_disc_int - p2p->min_disc_int) + 1) +
p2p->min_disc_int) * 100;
if (p2p->max_disc_tu >= 0 && tu > (unsigned int) p2p->max_disc_tu)
tu = p2p->max_disc_tu;
if (!dev_disc && tu < 100)
tu = 100; /* Need to wait in non-device discovery use cases */
if (p2p->cfg->max_listen && 1024 * tu / 1000 > p2p->cfg->max_listen)
tu = p2p->cfg->max_listen * 1000 / 1024;
if (tu == 0) {
p2p_dbg(p2p, "Skip listen state since duration was 0 TU");
p2p_set_timeout(p2p, 0, 0);
return;
}
//构造P2P Probe Response帧，当我们在Listen state收到其他设备发来的Probe Request帧后，wifi驱动将直接回复此处设置的 P2P Probe Response帧。
ies = p2p_build_probe_resp_ies(p2p, NULL, 0);
if (ies == NULL)
return;
p2p->pending_listen_freq = freq;
p2p->pending_listen_sec = 0;
p2p->pending_listen_usec = 1024 * tu;
//start_listen指向 wpas_start_listen 函数
if (p2p->cfg->start_listen(p2p->cfg->cb_ctx, freq, 1024 * tu / 1000,
ies) < 0) {
p2p_dbg(p2p, "Failed to start listen mode");
p2p->pending_listen_freq = 0;
}
wpabuf_free(ies);
}
在来看p2p_connect函数，其代码如下所示
这里面有3个重要的知识点
1、是 breaker值在每次发起P2P_CONNECT时都取反一次，这样做的目的是在双方的Intent值相同的情况下，多次协商时，双方都有机会做GO。并且在发送Request时才填入自己的breaker值，在回应Response时，是把对方的breaker值取反后作为breaker值发送。
-
如果当前P2P还在扫描过程中，则设置start_after_scan为P2P_AFTER_SCAN_CONNECT标志，当scan结束后，在扫描结果处理流程中，该标志将通知P2P进入connect处理流程
-
p2p_connect_send发送GON Request帧
int p2p_connect(struct p2p_data *p2p, const u8 *peer_addr,
enum p2p_wps_method wps_method,
int go_intent, const u8 *own_interface_addr,
unsigned int force_freq, int persistent_group,
const u8 *force_ssid, size_t force_ssid_len,
int pd_before_go_neg, unsigned int pref_freq, u16 oob_pw_id)
{
struct p2p_device *dev;p2p_dbg(p2p, "Request to start group negotiation - peer=" MACSTR " GO Intent=%d Intended Interface Address=" MACSTR " wps_method=%d persistent_group=%d pd_before_go_neg=%d " "oob_pw_id=%u allow_6ghz=%d", MAC2STR(peer_addr), go_intent, MAC2STR(own_interface_addr), wps_method, persistent_group, pd_before_go_neg, oob_pw_id, p2p->allow_6ghz); //获取当前设备p2p dev设备的信息 dev = p2p_get_device(p2p, peer_addr); if (dev == NULL || (dev->flags & P2P_DEV_PROBE_REQ_ONLY)) { p2p_dbg(p2p, "Cannot connect to unknown P2P Device " MACSTR, MAC2STR(peer_addr)); return -1; } // 如果指定了工作频段，则需要判断是否支持该工作频段，否则return -1 if (p2p_prepare_channel(p2p, dev, force_freq, pref_freq, go_intent == 15) < 0) return -1; if (dev->flags & P2P_DEV_GROUP_CLIENT_ONLY) { if (!(dev->info.dev_capab & P2P_DEV_CAPAB_CLIENT_DISCOVERABILITY)) { p2p_dbg(p2p, "Cannot connect to P2P Device " MACSTR " that is in a group and is not discoverable", MAC2STR(peer_addr)); return -1; } if (dev->oper_freq <= 0) { p2p_dbg(p2p, "Cannot connect to P2P Device " MACSTR " with incomplete information", MAC2STR(peer_addr)); return -1; } /* * First, try to connect directly. If the peer does not * acknowledge frames, assume it is sleeping and use device * discoverability via the GO at that point. */ } p2p->ssid_set = 0; if (force_ssid) { wpa_hexdump_ascii(MSG_DEBUG, "P2P: Forced SSID", force_ssid, force_ssid_len); os_memcpy(p2p->ssid, force_ssid, force_ssid_len); p2p->ssid_len = force_ssid_len; p2p->ssid_set = 1; } dev->flags &= ~P2P_DEV_NOT_YET_READY; dev->flags &= ~P2P_DEV_USER_REJECTED; dev->flags &= ~P2P_DEV_WAIT_GO_NEG_RESPONSE; dev->flags &= ~P2P_DEV_WAIT_GO_NEG_CONFIRM; if (pd_before_go_neg) dev->flags |= P2P_DEV_PD_BEFORE_GO_NEG; else { dev->flags &= ~P2P_DEV_PD_BEFORE_GO_NEG; /* * Assign dialog token and tie breaker here to use the same * values in each retry within the same GO Negotiation exchange. */ dev->dialog_token++; if (dev->dialog_token == 0) dev->dialog_token = 1; dev->tie_breaker = p2p->next_tie_breaker; p2p->next_tie_breaker = !p2p->next_tie_breaker;//这里是对intent的值取反 } dev->connect_reqs = 0; dev->go_neg_req_sent = 0; dev->go_state = UNKNOWN_GO; p2p_set_dev_persistent(dev, persistent_group); p2p->go_intent = go_intent; os_memcpy(p2p->intended_addr, own_interface_addr, ETH_ALEN); if (p2p->state != P2P_IDLE) p2p_stop_find(p2p); dev->wps_method = wps_method; dev->oob_pw_id = oob_pw_id; dev->status = P2P_SC_SUCCESS; if (p2p->p2p_scan_running) { p2p_dbg(p2p, "p2p_scan running - delay connect send");/*
如果当前P2P还在扫描过程中，则设置start_after_scan为P2P_AFTER_SCAN_CONNECT标志，
当scan结束后，在扫描结果处理流程中，该标志将通知P2P进入connect处理流程。
*/
p2p->start_after_scan = P2P_AFTER_SCAN_CONNECT;
os_memcpy(p2p->after_scan_peer, peer_addr, ETH_ALEN);
return 0;
}
// 下面这个函数将发送GON Request帧
return p2p_connect_send(p2p, dev);
}
p2p_set_state和p2p_set_timeout记录了P2P: State和Timeout
void p2p_set_state(struct p2p_data *p2p, int new_state)
{
p2p_dbg(p2p, "State %s -> %s",
p2p_state_txt(p2p->state), p2p_state_txt(new_state));
p2p->state = new_state;
if (new_state == P2P_IDLE && p2p->pending_channel) {
p2p_dbg(p2p, "Apply change in listen channel");
p2p->cfg->reg_class = p2p->pending_reg_class;
p2p->cfg->channel = p2p->pending_channel;
p2p->pending_reg_class = 0;
p2p->pending_channel = 0;
}
}
void p2p_set_timeout(struct p2p_data *p2p, unsigned int sec, unsigned int usec)
{
p2p_dbg(p2p, "Set timeout (state=%s): %u.%06u sec",
p2p_state_txt(p2p->state), sec, usec);
eloop_cancel_timeout(p2p_state_timeout, p2p, NULL);
eloop_register_timeout(sec, usec, p2p_state_timeout, p2p, NULL);
}